An organic light emitting diode (OLED) has a structure in which a functional organic layer is interposed between a cathode and an anode, and produces highly energetic excitons by recombination of holes injected from the anode with electrons injected from the cathode. Then, the produced excitons are transferred to a ground state to generate light having a specific wavelength. Organic light emitting diodes have advantages of self-luminescence, rapid response, wide viewing angle, high definition, and durability.
However, organic light emitting diodes have problems of deterioration in performance and lifespan due to oxidation of organic materials and/or electrode materials caused by moisture or oxygen from outside or due to internal or external outgassing. To overcome such problems, various methods, such as coating with a photocurable sealing agent, attachment of a transparent or opaque hygroscopic agent, or provision of fits to a substrate having an organic light emitting diode formed thereon, have been proposed in the art.